Hello, I am doing my second floor bathroom renovation now. I removed all floor tiles and the toilet and have found my toilet drain pipe looks like this:
Question: After tiles are installed to fix my toilet flange for an old cust iron pipe-

or should I use the internal flange at it shown here:

Both of them have rubber ring which would expand and keep flange from rocking.

The rubber part is to create the seal so if there were a backup or for sewer gasses, the connection doesn't leak...your CI looks pretty corroded. I'd want to try a wire brush on it to clean things off, then decide if I could get a decent seal either inside or outside. If it's a 4" pipe, if you can get it cleaned up, either should work, but if it is a 3" pipe, you should only consider an external one. If there's enough there, a plumber could install a new leaded joint, too. Not usually something a typical homeowner has the tools necessary to complete.

May I ask you how would you :
A. remove lead closet arm? Use hammer with a chisel? Cut it at the metal pipe flange intake and then heat it up and take it out?
B. secure plastic ABS closet bend pipe to the metal drain?

I waste a few drill bits going at the lead until I have enough out that I can pry it with a flat blade screwdriver. Eventually you can pull the lead out and the oakum, which is like a rope behind the lead. That prevents the poured lead from dripping down the pipe.

I find the correct size tyseal or Fernco for the hub and tap in either pipe or a 4x3 flush bush. I taper the end of the pipe or bush, lube it with liquid soap and tap it in using a wooden block and a hammer.
Not an easy job though. Sometimes things are pretty snug.
I like to use a 4x3 spigot closet flange that allows for a tigher bend using a 4" hub closet flange. Your standard bends take up too much space when replacing a lead bend.

They left the brass ferrule and the lead in the fitting, and then they used a no-hub coupling. Some plumbers do that.
Like they mentioned in the video, to do it my way would have been more work.

Click to expand...

Would it be appropriate to ask how much would you charge to do it your way? I just would like to figure out how much it will cost me if I hire a plumber here.

Also if you would not recommend to use external or internal flange with a compression fitting, then why did they use a no-hub coupling? Wouldn't this no-hub coupling create any compression to the lead pipe?

They were using a CAST IRON bend and pipe. They cut the lead off 2" from the stack.

I charge about $500 to replace a bend. And I don't really like doing them.

Click to expand...

Home repair book would say that banded couplings may be used to connect new plastic pipe to remaining cast iron pipe. How much confidence would you have for the connection of the new plastic pipe to remaining lead pipe?

May be I should just insert 3'' plastic pipe with rubber part (is to create the seal so if there were a backup or for sewer gasses)
into remaining lead pipe instead of using banded coupling?

The only way to reuse a lead bend is if the end is not cracked and it is long enough to seal over a new flange ring. You need to bite the bullet and do this right. You will not be able to make a reliable, water AND gas tight connection to what's left of the lead pipe. You may not notice any leaks until there's a clog, then it starts dripping all over the floor under the toilet. If you're out of your comfort zone, it's time for a plumber.

The picture you posted showed the wrong sized shielded coupling. The cast is thinner than the plastic pipe. They make proper couplings for those. They don't really make a good one to go on the lead though. Your idea of pushing a spigot pipe into cast is "interesting".
It's also interesting how many ways a job can be done, many of them I wouldn't allow to be done in my home. Thank goodness for my customers that I treat them the same way.

I cut lead pipe at some distance from the CI pipe intake, as I discovered brass ferrule (shown by red arrow) right at the CI pipie intake.
It looks like that original scenario for removing lead pipe compleately from the CI intake may not work for me very easy way, as I have to drill out not just lead but brass ferrule out from the CI intake.

The furrule was to maintain the shape of the lead bend at the hub. Once you drill enough holes in the lead that is caulked around the perimeter of the hub, you can pull it out in a few pieces and the joint will come apart.

It's not brain surgery, it's more like pounding a few nails. As long as you don't pound on the hub with a sledgehammer, there is not much there that you can do wrong.

The brass ferrule is the reason why they could make a solid connection to the CI, and you can't make one at the other end which is only lead. WIth it cut off there, you could take a hacksaw blade and cut a notch through it on the inside in a couple of places, then peel it out rather than drilling out the lead on the outside. It's a pain, but if you make the lead into swiss cheese, you will be able to pry it out of there.